The book is divided into four seperate chapters: the Palaeozoic, the Mesozoic, the Cenozoic, and a section at the back of the book with a timeline and family tree showing the respective positions of each animal in the tome. 111 creatures are featured, as well as a hominid species, Homo floresiensis. This was probably because it was an exciting new species discovered close to publication.
Each profile starts with a fact file that lists simple facts such as length, location, and diet of the animal. Then there is a detailed description of each animal, accompanied by a full-color screenshot of the creature from the series (or, in the case of Homo floresiensis, an illustration). Several prehistoric animals from the series never before seen in mainstream books are covered, such as Megalograptus, Brontoscorpio, and Hyneria.